In a sample and hold application, a switch receives a voltage at its input and, during a sampling period (sample), delivers that voltage to a capacitor connected to its output terminal. During the hold period (hold), the switch is open (that is to say not conducting). Because of leakage currents, the capacitor can, depending of the case, either be discharged to ground or be charged up to the power supply voltage, which therefore creates instability of the voltage present across the terminals of the capacitor.